Grenoble INP, CNRS, GIPSA-Lab UMR 5216, Univ. Grenoble Alpes, Grenoble, France.
Grenoble INP, CNRS, TIMC-IMAG UMR 5525, Univ. Grenoble Alpes, Grenoble, France.
PLoS One. 2020 Apr 14;15(4):e0231484. doi: 10.1371/journal.pone.0231484. eCollection 2020.
This study aimed to evaluate the role of motor control immaturity in the speech production characteristics of 4-year-old children, compared to adults. Specifically, two indices were examined: trial-to-trial variability, which is assumed to be linked to motor control accuracy, and anticipatory extra-syllabic vowel-to-vowel coarticulation, which is assumed to be linked to the comprehensiveness, maturity and efficiency of sensorimotor representations in the central nervous system.
Acoustic and articulatory (ultrasound) data were recorded for 20 children and 10 adults, all native speakers of Canadian French, during the production of isolated vowels and vowel-consonant-vowel (V1-C-V2) sequences. Trial-to-trial variability was measured in isolated vowels. Extra-syllabic anticipatory coarticulation was assessed in V1-C-V2 sequences by measuring the patterns of variability of V1 associated with variations in V2. Acoustic data were reported for all subjects and articulatory data, for a subset of 6 children and 2 adults.
Trial-to-trial variability was significantly larger in children. Systematic and significant anticipation of V2 in V1 was always found in adults, but was rare in children. Significant anticipation was observed in children only when V1 was /a/, and only along the antero-posterior dimension, with a much smaller magnitude than in adults. A closer analysis of individual speakers revealed that some children showed adult-like anticipation along this dimension, whereas the majority did not.
The larger trial-to-trial variability and the lack of anticipatory behavior in most children-two phenomena that have been observed in several non-speech motor tasks-support the hypothesis that motor control immaturity may explain a large part of the differences observed between speech production in adults and 4-year-old children, apart from other causes that may be linked with language development.
本研究旨在评估运动控制不成熟在 4 岁儿童言语产生特征中的作用，与成人进行比较。具体而言，研究了两个指标：音高变化的逐次试验变异性，该指标与运动控制精度有关；音节前超音段元音-元音协同发音的预测性，该指标与中枢神经系统中感觉运动表征的全面性、成熟度和效率有关。
本研究对 20 名儿童和 10 名成人的发音数据进行了声学和发音（超声）记录，所有参与者均为加拿大法语母语者，他们在发孤立元音和元音-辅音-元音（V1-C-V2）序列时完成了任务。在孤立元音中测量了逐次试验变异性。通过测量与 V2 变化相关的 V1 的变异性模式，评估了 V1-C-V2 序列中音节前的预测性协同发音。为所有参与者报告了声学数据，为 6 名儿童和 2 名成人报告了发音数据。
儿童的逐次试验变异性显著较大。成人始终在 V1 中发现 V2 的系统性和显著的预测性，但在儿童中很少见。仅当 V1 为 /a/时，且仅在前后维度上，儿童才会出现显著的预测性，而且幅度比成人小得多。对个体说话者的更详细分析表明，一些儿童在这个维度上表现出成人样的预测性，而大多数儿童则没有。
大多数儿童的逐次试验变异性较大，缺乏预测性行为，这两个现象在几项非言语运动任务中都有观察到，除了可能与语言发展有关的其他原因外，这一现象支持了运动控制不成熟可能在很大程度上解释了成人和 4 岁儿童言语产生差异的假说。
